On Facebook, at least, Sen. Marco Rubio, R-Fla., is the least talked about on sitting senator running for president.

In the last month leading up to Thursday night’s Fox Business debate, 1.49 million people in the United States posted about, shared, like or commented on content about Rubio over 4.5 million times, according to data released by the social media platform. Compare that with Donald Trump, who is leading candidates in Facebook engagement — 18.9 million people have posted about, shared, liked or comments on content about the business mogul more than 105 million times in the last month.